Typically, billet-grinding machines include a stand carrying a grinding wheel arranged adjacent to a table for the billet to be ground. The grinding wheel is mounted on a horizontal axle, which is driven by a motor, and the grinding wheel is movable in a vertical direction as well as in a horizontal direction across the workpiece. Typically, the grinding wheel is supported on the stand via a linkage so that it is movable in the vertical and horizontal directions. Usually, the table is capable of reciprocating in a horizontal plane and parallel with the axle of the grinding wheel.
The billets are ground so as to remove or eliminate cracks and the irregularities in the surface layer of the billet. Otherwise, these cracks and irregularities would substantially deteriorate the quality of further work performed on the billet. However, the material of the billet is expensive, and therefore, the grinding must be accurately controlled so as to minimize the amount of material removed from the surface of the billet. It is therefore advantageous to maintain the amount of material being removed constant. However, this requires that the contact force between the grinding wheel and the billet must be maintained constant during the horizontal movement of the grinding wheel. This objective can be achieved, for example, by directly maintaining constant the pressure in a hydraulic cylinder connected to the suspension arrangement of the grinding wheel or indirectly by controlling the pressure in the hydraulic cylinder by means of the power consumption of the motor driving the grinding wheel.
However, there have been drawbacks to both of these methods. In the former case, difficulties arise because the suspension of the grinding wheel is of such a nature that a constant pressure in the hydraulic cylinder produces a varying contact force between the billet and the grinding wheel as it moves. In the latter case, an extensive and complicated control apparatus is required for rendering a satisfactory result. A typical example of a prior art grinding machine is disclosed in U.S. Pat. No. 2,982,056.
Broadly, it is an object of the present invention to provide an improved grinding machine which overcomes one or more of the aforesaid problems. Specifically, it is within the contemplation of the present invention to provide a grinding machine which includes a hydraulic cylinder for determining the contact force with the billet and is arranged so that a constant hydraulic pressure corresponds directly to a constant contact force between the grinding wheel and the billet.